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Abstract:

A portable radio-frequency identifier (RFID) reading terminal can
comprise a microprocessor, a memory, an RFID reading device, and a
display. The portable EIR terminal can be configured, responsive to
successfully reading a plurality of RFID tags attached to a plurality of
items sustained by a physical structure, to group the plurality of read
RFID tags into zero or more clusters, by correlating quantities of RFID
tags read within several time periods to spatial positions of the
coverage shapes of the RF signals transmitted by the RFID reading device
during the several time periods. The EIR terminal can be further
configured to determine the spatial positions of the RFID signal coverage
shapes based on the spatial positions and orientations of the portable
EIR terminal during the several time periods. The EIR terminal can be
further configured to display a quantity of RFID tags within each cluster
overlaid over an image.

Claims:

1. A portable encoded information reading (EIR) terminal comprising: a
microprocessor; a memory; an RFID reading device; a display; wherein said
portable EIR terminal is configured, responsive to successfully reading a
plurality of RFID tags attached to a plurality of items sustained by a
physical structure, to group said plurality of read RFID tags into zero
or more clusters, by correlating quantities of RFID tags read within
several time periods to spatial positions of coverage shapes of RF
signals transmitted by said RFID reading device during said several time
periods, said spatial positions of said coverage shapes of said RFID
signals determined based on spatial positions and orientations of said
portable EIR terminal during said several time periods; wherein said
portable EIR terminal is further configured to display a quantity of RFID
tags within each cluster overlaid over an image of said physical
structure, with a visual reference to a fragment of said physical
structure corresponding to spatial positions of one or more RFID tags
comprised by each cluster.

2. The portable EIR terminal of claim 1, further configured to display a
scan trace overlaid over said image of said physical structure; wherein
said scan trace is provided by a line comprising a plurality of time
varying points, each point being defined by a projection onto a chosen
plane at a given moment in time of said coverage shape of said RF signal
transmitted by said RFID reading device.

3. The portable EIR terminal of claim 1, further comprising a
two-dimensional imager; wherein said portable EIR terminal is further
configured to determine a spatial position of said RF signal coverage
shape based on a position and orientation of said RF antenna relatively
to a position of a field of view of said two-dimensional imager.

4. The portable EIR terminal of claim 1, further comprising a motion
sensing device; wherein said portable EIR terminal is further configured
to determine a change of a spatial position and orientation of said RF
signal coverage shape based on motion sensing data received from said
motion sensing device.

5. The portable EIR terminal of claim 1, further comprising a motion
sensing device; wherein said motion sensing device comprises three or
more accelerometers configured to measure proper acceleration values of
said EIR terminal along three mutually perpendicular axes.

6. The portable EIR terminal of claim 1, further configured to receive an
image of said physical structure from an external computer.

7. The portable EIR terminal of claim 1, further configured to receive a
description of a physical structure; wherein said portable EIR terminal
is further configured to create an image of said physical structure based
on said description.

8. The portable EIR terminal of claim 1, further comprising a
two-dimensional imager; wherein said portable EIR terminal is further
configured to acquire an image of said physical structure using said
two-dimensional imager.

9. The portable EIR terminal of claim 1, further configured to transmit
to an external computer at least one of: a list of read RFID tags, a
count of read RFID tags, a count of clusters of RFID tag bearing items, a
list of items in each cluster, and/or a list of locations of clusters to
an external computer.

[0002] RFID methods are widely used in a number of applications, including
smart cards, item tracking in manufacturing, inventory management in
retail, etc. An RFID tag can be attached, e.g., to an inventory item. An
EIR terminal can be configured to read the memory of an RFID tag attached
to an inventory item.

SUMMARY OF THE INVENTION

[0003] In one embodiment, there is provided a portable radio-frequency
identifier (RFID) reading terminal comprising a microprocessor, a memory,
an RFID reading device, and a display. The portable EIR terminal can be
configured, responsive to successfully reading a plurality of RFID tags
attached to a plurality of items sustained by a physical structure, to
group the plurality of read RFID tags into zero or more clusters, by
correlating quantities of RFID tags read within several time periods to
spatial positions of the coverage shapes of the RF signals transmitted by
the RFID reading device during the several time periods. The EIR terminal
can be further configured to determine the spatial positions of the RFID
signal coverage shapes based on the spatial positions and orientations of
the portable EIR terminal during the several time periods. The EIR
terminal can be further configured to display a quantity of RFID tags
within each cluster overlaid over an image of the physical structure,
with a visual reference to a fragment of the physical structure
corresponding to the spatial positions of the RFID tags comprised by each
cluster.

[0004] In one embodiment, the portable EIR terminal can be further
configured to display a scan trace overlaid over the image of the
physical structure. The scan trace can be provided by a line comprising a
plurality of time varying points, each point being defined by a
projection onto a chosen plane at a given moment in time of the coverage
shape of the RF signal transmitted by the RFID reading device.

[0005] In one embodiment, the portable EIR terminal can further comprise a
two-dimensional imager, and can be further configured to determine the
spatial position of the RF signal coverage shape based on the position
and orientation of the RF antenna relatively to the position of the field
of view of the two-dimensional imager.

[0006] In one embodiment, the portable EIR terminal can further comprise a
motion sensing device, and can be further configured to determine a
change of the spatial position and orientation of the RF signal coverage
shape based on the motion sensing data received from the motion sensing
device. In a further aspect, the motion sensing device can comprise three
or more accelerometers configured to measure proper acceleration values
of the EIR terminal along three mutually perpendicular axes.

[0007] In one embodiment, the portable EIR terminal can be further
configured to receive an image of the physical structure from an external
computer.

[0008] In one embodiment, the portable EIR terminal can be further
configured to receive a description of a physical structure, and can be
further configured to create an image of the physical structure based on
the description.

[0009] In one embodiment, the portable EIR terminal can further comprise a
two-dimensional imager, and can be further configured to acquire an image
of the physical structure using the two-dimensional imager.

[0010] In one embodiment, the portable EIR terminal can be further
configured to transmit a list of read RFID tags, a count of read RFID
tags, a count of clusters of RFID tag bearing items, a list of items in
each cluster, and/or a list of locations of clusters to an external
computer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For the purpose of illustrating the invention, the drawings show
aspects of one or more embodiments of the invention. However, it should
be understood that the present invention is not limited to the precise
arrangements and instrumentalities shown in the drawings, wherein:

[0017] FIGS. 6a-6b schematically illustrate determining a spatial position
of the RF signal coverage shape based on the position and orientation of
an RF antenna relatively to the position of the field of view of a
two-dimensional imager;

[0019] The drawings are not necessarily to scale, emphasis instead
generally being placed upon illustrating the principles of the invention.
In the drawings, like numerals are used to indicate like parts throughout
the various views.

DETAILED DESCRIPTION OF THE INVENTION

[0020] RFID reading devices usually offer improved efficiency over barcode
scanning devices for retail inventory, by being capable of reading
multiple RFID tags that are within range of the RF signal transmitted by
an RFID reading device. A downside to this multiple-read capability is
lack of scanned items localization, due to insufficient correlation
between where the RFID reader is located or oriented, and the RFID tags
being read. Retail inventory management typically requires more than 90%
of the RFID tags present in a department to be successfully acquired
during the inventory process. When this high accuracy is not achieved, it
is necessary to rescan the entire department, since the locations of any
unread RFID tags are unknown.

[0021] Item tracking and/or inventory control can be implemented by
placing an RFID tag on each inventory item. The EIR terminal can comprise
at least one RFID reading device which can be configured to read and/or
modify a memory of an RFID tag containing an encoded message. The RFID
reading device can transmit and/or receive radio frequency (RF) signals
to and from RFID tags attached to inventory items. Each RFID tag can
store the tag identifier in its memory. An RFID tag attached to an
inventory item can further store in the tag's memory a product code of
the item, an EPC (Electronic Product Code) of the item, and/or at least
one alphanumeric string identifying the item.

[0022] The RFID reading device can be further configured to output decoded
message data corresponding to the encoded message, e.g., decoded message
data containing identifiers of the items to which the RFID tags are
attached. The EIR terminal can be configured to store in its memory
and/or transmit to an external computer the item identifiers received
from the plurality of RFID tags.

[0023] The EIR terminal can read RFID tags from a range of distances and
various terminal orientations with respect to an RFID tag being read. To
further improve the reliability of scanning operations and the terminal's
operator experience, the EIR terminal can be configured to display the
quantity of successfully read RFID tags overlaid over an image of a
physical structure (e.g., a shelving unit) sustaining the items bearing
the RFID tags (e.g., inventory items at a manufacturing, retail or a
storage facility). In a further aspect, the portable EIR terminal can be
configured to group a plurality of successfully read RFID tags into zero
or more clusters, and display the quantities of RFID tags within each
cluster with a visual reference to a fragment of the physical structure
sustaining items bearing the RFID tags comprised by each cluster, as
schematically shown in FIG. 1.

[0024] Such a capability provides increased operational efficiency of RFID
tag reading for retail inventory management. Various embodiments of the
EIR terminal can be used in a numerous applications, including but not
limited to, item tracking in manufacturing, storage, and retail,
real-time inventory control systems, etc.

[0025] As described in the commonly assigned U.S. patent application Ser.
No. 13/359,005 entitled "Portable RFID Reading Terminal with Visual
Indication of Scan Trace" filed on Jan. 26, 2012, which is incorporated
herein by reference in its entirety, an EIR terminal can be configured to
receive an expected count of inventory items or an expected inventory
list of items of interest stored within a storage, manufacturing, and/or
retail facility. The EIR terminal can be further configured to reconcile
the inventory of items stored within a storage, manufacturing, and/or
retail facility against the expected count of inventory items or the
expected inventory list by reading the RFID tags attached to the
inventory items. As used herein, "inventory list" shall refer to a
collection of item descriptions, each item description comprising at
least the item identifier.

[0026] As described in the commonly assigned U.S. Patent Application
(number not yet assigned) attorney docket number H0032657, entitled
"System and Method for Calibration and Mapping of Real-Time Location
Data" filed concurrently herewith, which is incorporated herein by
reference in its entirety, an EIR terminal configured to read RFID tags
can be augmented with an imaging device, positioning package, including
but not limited to, a 3-axis (3 dimensional) accelerometer package, and a
9-DOF (degree of freedom) IMU (Inertial Measurement Unit) containing a
3-axis accelerometer, a 3-axis magnetometer, and 3-axis gyroscope
sensors, to acquire movement and position calibration data regarding the
motion of the EIR terminal.

[0027] At any moment in time, the RF signal coverage emitted by an EIR
terminal can be defined by a 3D shape, as schematically shown in FIG. 2.
The form and size of the 3D shape defining the RF signal coverage can
depend, among other factors, on the RFID transmit power level and the
number and configuration of the RF antennas employed by the RFID reading
device. In one embodiment, the RF signal coverage shape can be provided
by a sphere 2020. In another embodiment, the RF signal coverage shape can
be provided by an ellipsoid. In a yet another embodiment, the RF signal
coverage shape can be provided by a cone. In some embodiments, the RF
signal coverage shape can have an irregular shape, the irregularity being
caused, for example, by the EIR terminal's having two or more antennas
which can transmit RF signals of different power. In a further aspect,
the EIR terminal can have a capability of determining the current
transmit power of each of two or more antennas, and determine the
expected RF signal coverage shape.

[0028] At any given moment in time, a target scan area by an EIR terminal
can be visualized as a projection 2040 of the 3D RF signal coverage shape
2020 onto an arbitrarily chosen plane 2050, including an imaginary plane.
In one embodiment, the EIR terminal can be further configured to display
a visual scan trace overlaid over an image of the physical structure
(e.g., a shelving unit) sustaining a plurality of items bearing RFID tags
(e.g., retail items). For a moving EIR terminal, the visual scan trace
can be provided by a line defined by a multitude of time varying points,
each point being a projection 2040 of the 3D RF signal coverage shape
2020 onto the arbitrarily chosen plane 2050 at a given moment in time. In
a further aspect, the imaginary plane onto which the visual scan trace is
projected can be chosen to intersect a physical structure (e.g., a shelf)
containing the inventory items, and thus the scan trace can be overlaid
over an image of the physical structure.

[0029] Component-level diagram of one embodiment of the EIR terminal is
now being described with references to FIG. 3. The EIR terminal 100 can
comprise at least one microprocessor 310 and a memory 320, both coupled
to the system bus 370. The microprocessor 310 can be provided by a
general purpose microprocessor or by a specialized microprocessor (e.g.,
an ASIC). In one embodiment, EIR terminal 100 can comprise a single
microprocessor which can be referred to as a central processing unit
(CPU). In another embodiment, EIR terminal 100 can comprise two or more
microprocessors, for example, a CPU providing some or most of the EIR
terminal functionality and a specialized microprocessor performing some
specific functionality. A skilled artisan would appreciate the fact that
other schemes of processing tasks distribution among two or more
microprocessors are within the scope of this disclosure.

[0030] EIR terminal 100 can further comprise a communication interface 340
communicatively coupled to the system bus 370. In one embodiment, the
communication interface can be provided by a wireless communication
interface. The communication interface can be configured to support, for
example, but not limited to, the following protocols: at least one
protocol of the IEEE 802.3/IEEE 802.11/802.15/802.16 protocol family, at
least one protocol of the HSPA/GSM/GPRS/EDGE protocol family, TDMA
protocol, UMTS protocol, LTE protocol, and/or at least one protocol of
the CDMA/1xEV-DO protocol family.

[0031] EIR terminal 100 can further comprise a battery 356. In one
embodiment, the battery 356 can be provided by a replaceable rechargeable
battery pack. The EIR terminal 100 can further comprise a GPS receiver
380. The EIR terminal 100 can further comprise at least one connector 390
configured to receive a subscriber identity module (SIM) card.

[0032] The EIR terminal 100 can further comprise an imaging device 330,
provided, for example, by a two-dimensional imager. The EIR terminal 100
can further comprise a motion sensing device 354.

[0033] The EIR terminal 100 can further comprise an RFID reading device
333. In one embodiment, the RFID reading device 333 can be configured to
read a memory of an RFID tag containing an encoded message and to output
raw message data containing the encoded message. In another embodiment,
the RFID reading device 333 can be configured to read a memory of an RFID
tag containing an encoded message and to output decoded message data
corresponding to the encoded message. As used herein, "message" is
intended to denote a bit sequence or a character string comprising
alphanumeric and/or non-alphanumeric characters. An encoded message can
be used to convey information, such as identification of the source and
the model of an item, for example, in an EPC code.

[0034] In one embodiment, the EIR terminal 100 can further comprise a
graphical user interface including a display adapter 175 and a keyboard
179. In one embodiment, the EIR terminal 100 can further comprise an
audio output device, e.g., a speaker 181.

[0035] It is not necessary that a device's primary function involve
reading RFID tags in order to be considered an EIR terminal; for example,
a cellular telephone, a smart phone, a PDA, or other portable computing
device that is capable of reading RFID tags can be referred to as an EIR
terminal for purposes of this disclosure.

[0036] In a further aspect, the EIR terminal can be incorporated in a data
collection system. One embodiment of the data collection system,
schematically shown in FIG. 4, can include a plurality of EIR terminals
100a-100z in communication with a plurality of interconnected networks
110a-110z.

[0037] An EIR terminal 100a-100z can establish a communication session
with an external computer 171. In one embodiment, network frames can be
exchanged by the EIR terminals 100a-100z and the external computer 171
via one or more routers 140, access points 135, and other infrastructure
elements. In another embodiment, the external computer 171 can be
reachable by the EIR terminal 100m via a local area network (LAN). In a
yet another embodiment, the external computer 171 can be reachable by the
EIR terminal 100 via a wide area network (WAN). In a yet another
embodiment, the external computer 171 can be reachable by the EIR
terminal 100 directly (e.g., via a wired or wireless interface). A
skilled artisan would appreciate the fact that other methods of providing
interconnectivity between the EIR terminal 100 and the external computer
171 relying upon LANs, WANs, virtual private networks (VPNs), and/or
other types of network are within the scope of this disclosure.

[0038] A "computer" herein shall refer to a programmable device for data
processing and control, including a central processing unit (CPU), a
memory, and at least one communication interface. For example, in one
embodiment, a computer can be provided by a server running a single
instance of a multi-tasking operating system. In another embodiment, a
computer can be provided by a virtual server, i.e., an isolated instance
of a guest operating system running within a host operating system. A
"network" herein shall refer to a set of hardware and software components
implementing a plurality of communication channels between two or more
computers. A network can be provided, e.g., by a local area network
(LAN), or a wide area network (WAN). While different networks can be
designated herein, it is recognized that a single network as seen from
the application layer interface to the network layer of the OSI model can
comprise a plurality of lower layer networks, i.e., what can be regarded
as a single Internet Protocol (IP) network, can include a plurality of
different physical networks.

[0039] The communications between the EIR terminal 100 and the external
computer 171 can comprise a series of requests and responses transmitted
over one or more TCP connections. A skilled artisan would appreciate the
fact that using various transport and application level protocols is
within the scope and the spirit of the invention.

[0040] In one embodiment, at least one of the messages transmitted by the
EIR terminal 100 can include decoded message data corresponding to an
RFID label attached to an inventory item. For example, an EIR terminal
can transmit a request to the external computer to retrieve product
information corresponding to a product identifier encoded by an RFID tag
attached to a retail item, or to transmit an item tacking record for an
item identified by an RFID tag attached to the item.

[0041] As noted herein supra, the EIR terminal 100 can be configured to
receive from the external computer 171 information including, but not
limited to an inventory list containing item identifiers, or count, of
items stored within a storage, manufacturing, and/or retail facility. The
inventory list or count can further contain storage location information
of specific items. The EIR terminal 100 can be further configured to
transmit to the external computer 171 information including, but not
limited to a list of read RFID tags, a count of read RFID tags, a count
of clusters of RFID tag bearing items, a list of items in each cluster,
and/or a list of locations of clusters.

[0042] In one embodiment, the EIR terminal 100 can be configured to
receive from the external computer 171 one or more images of physical
structures sustaining inventory items bearing RFID tags. An image can be
provided, for example, by a photographical image or by a rendered
outline.

[0043] As noted herein supra, the EIR terminal 100 can be configured,
responsive to successfully reading a plurality of RFID tags attached to a
plurality of items sustained by a physical structure, to group the RFID
tags into zero or more clusters, and display a quantity of RFID tags
within each cluster overlaid over an image of the physical structure,
with a visual reference to a fragment of the visual structure
corresponding to spatial positions of the RFID tags comprised by each
cluster.

[0044] In a further aspect, the EIR terminal can be configured to store in
its memory the identifiers of successfully read RFID tags together with
timestamps of the read events. The EIR terminal can use the stored
information to correlate quantities of RFID tags read within several time
periods to spatial positions of the coverage shapes of the RFID signals
transmitted by the RFID reading device. Based on the correlation, the EIR
terminal can group the RFID tags into several clusters, as schematically
shown in FIGS. 5a-5b. FIG. 5a illustrates eight stacks of RFID bearing
items sustained by a shelving unit. FIG. 5b illustrates a graph showing
the number of RFID tags that were read over the time periods t0-16. Based
on the graph of FIG. 5b, eight clusters of RFID tags can be revealed.

[0045] In a further aspect, the EIR terminal can be configured to
determine the spatial positions of the RFID signal coverage shapes based
on spatial positions and orientations of the terminal during the several
time periods.

[0046] In a further aspect, the EIR terminal can be configured to display
the quantities of RFID tags within each cluster overlaid over an image of
the physical structure, with a visual reference to a fragment of the
physical structure (e.g., a shelf of a shelving unit) corresponding to
spatial positions of the RFID tags comprised by each cluster.

[0047] In one embodiment, the EIR terminal can comprise a two-dimensional
imager. The EIR terminal can be configured to determine a spatial
position of the RF signal coverage shape based on the known position and
orientation of the RF antenna relatively to the position of the field of
view (FOV) of the two-dimensional imager, as schematically shown in FIGS.
6a-6b.

[0048] As noted herein supra, at any given moment in time, a target scan
area by an EIR terminal can be visualized as a projection 2040 of the 3D
RF signal coverage shape 2020 onto an arbitrarily chosen plane 2050,
including an imaginary plane. The plane 2050 can represent an arbitrary
chosen plane, e.g., a plane intersecting a physical structure hosting one
or more inventory items. The RF antenna can be oriented relatively to the
view finder in such a way that the central axis 5010 of the field of view
of the imager would be parallel to the central axis 5020 of the RF signal
coverage shape by the antenna. Reducing the distance between the EIR
terminal and the plane 2050 and/or increasing the RF transmit power level
results in a larger projection of the RF signal coverage area onto the
plane 5020, as schematically shown in FIGS. 6a-6b. In the example of FIG.
6b, the lesser distance and/or the greater transmit power level results
in a larger projection RF signal coverage area onto the plane 2050. The
projection of the RF signal coverage shape onto the plane 2050 can be
entirely within the FOV of the two-dimensional imager, as schematically
shown in FIG. 6a, or can be partially outside of the FOV of the
two-dimensional imager, as schematically shown in FIG. 6b.

[0049] Based on the expected shape of the signal coverage and the distance
and orientation of the RF antenna to a physical structure (e.g., depicted
as plane 2050 in FIG. 2) containing the inventory items, the EIR terminal
can determine and display the projection of the 3D RF signal coverage
shape onto the plane defined by the physical structure.

[0050] In another embodiment, the EIR terminal can comprise a motion
sensing device and can be configured to determine the change of the
spatial position and orientation of the RF signal coverage shape based on
the motion sensing data received from the motion sensing device. In one
illustrative embodiment, the motion sensing device can comprise three or
more accelerometers configured to measure proper acceleration values of
the EIR terminal along three mutually perpendicular axes.

[0051] As noted herein supra, in one embodiment, the EIR terminal 100 can
be further configured to display the quantities of RFID tags by cluster
and/or a scan trace overlaid over an image of a physical structure (e.g.,
a shelf) containing one or more scanned items and possibly one or more
items yet to be scanned. In one embodiment, the image of the physical
structure containing the inventory items can be received by the EIR
terminal 100 over the network from an external computer 171. In another
embodiment, the EIR terminal 100 can comprise a two-dimensional imager,
and the image of the physical structure containing the inventory items
can be acquired by the two-dimensional imager. In another embodiment, the
image of the physical structure is drawn, with appropriate detail, on the
EIR terminal display, based on a description of the physical structure
received by the terminal 100 via the user interface, from an external
peripheral device or from an external computer.

[0052] In a further aspect, RFID reading device 333 can be compliant with
EPC® Class-1 Generation-2 UHF RFID Protocol for Communications at 860
MHz-960 MHz by EPCglobal, commonly known as the "Gen 2" standard, which
defines physical and logical requirements for a passive-backscatter,
interrogator-talks-first (ITF) RFID system operating in the 860 MHz-960
MHz frequency range.

[0053] In one embodiment, EIR terminal 100 can transmit information to a
passive RFID tag by modulating an RF signal in the 860-960 MHz frequency
range. An RFID tag can receive both information and operating energy from
the RF signal transmitted by the EIR terminal 100. EIR terminal 100 can
receive information from the RFID tag by transmitting a continuous-wave
(CW) RF signal to the RFID tag. "Continuous wave" can refer to any
waveform transmitted by an RFID reading device and suitable to power a
passive RFID tag, e.g., a sinusoid at a given frequency. The RFID tag can
respond by modulating the reflection coefficient of its antenna, thus
backscattering an information signal to the EIR terminal 100. In one
embodiment, the RFID tag can modulate the reflection coefficient of its
antenna only responsive to receiving an RFID signal from EIR terminal
100.

[0054] In a further aspect, EIR terminal 100 can be configured to send
information to one or more RFID tags by modulating an RF carrier using
double-sideband amplitude shift keying (DSB-ASK), single-sideband
amplitude shift keying (DSB-ASK), or phase-reversal amplitude
shift-keying (PR-ASK) using a pulse-interval encoding (PIE) format. RFID
tags can receive their operating energy from the same modulated RF
carrier.

[0055] The EIR terminal 100 can be configured to receive information from
an RFID tag by transmitting an unmodulated RF carrier and listening for a
backscatter reply. RFID tags can transmit information by
backscatter-modulating the amplitude and/or phase of the RFID carrier.
RFID tags can encode the backscattered data using, e.g., FM0 baseband or
Miller modulation of a subcarrier at the data rate. The encoding method
to be employed by an RFID tag can be selected by the EIR terminal 100.

[0056] In another aspect, EIR terminal can establish one or more sessions
with one or more RFID tags. An RFID tag can support at least one
session-dependent flag for every session. The session-dependent flag can
have two states. An RFID tag can invert a session-dependent flag
responsive to receiving a command from EIR terminal 100. Tag resources
other than session-dependent flags can be shared among sessions. In
another aspect, an RFID tag can support a selected status flag indicating
that the tag was selected by the EIR terminal 100.

[0057] Responsive to receiving an interrogation signal transmitted by the
EIR terminal 100, an RFID tag can transmit a response signal back to EIR
terminal 100. The response signal can contain useful data, e.g., an
Electronic Product Code (EPC) identifier, or a tag identifier (TID). The
response signal can include a representation of a binary string, at least
part of which is equal to at least part one of the specified one or more
target item identifiers.

[0058] In one embodiment, EIR terminal can implement EPC® Class-1
Generation-2 UHF RFID Protocol for Communications at 860 MHz-960 MHz by
EPCglobal. The EIR terminal 100 can interrogate RFID tags using the
commands described herein infra.

[0059] Select command can be used by the EIR terminal 100 to select a
particular RFID tag population for the subsequent inventory round. Select
command can be applied successively to select a particular tag population
based on user-specified criteria. Select command can include the
following parameters:

[0060] Target parameter indicates whether Select
command modifies a tag's SL flag or Inventoried flag, and in the latter
case it further specifies one of four available sessions (S0, . . . ,
S3);

[0061] Action parameter indicates whether matching tags assert or
deassert SL flag, or set their Inventoried flag to A or B state; tags
conforming to the contents of MemBank, Pointer, Length, and Mask
parameters are considered to be matching;

[0062] Mask parameter contains
a bit string that a tag should compare to a memory location specified by
MemBank, Pointer, and Length parameters;

[0065] Length parameter specifies the number of bits of memory for
Mask; if Length is equal to zero, all tags are considered matching.

[0066] Inventory command set can be used by the EIR terminal 100 to single
out one or more individual tags from a group of RFID tags. A tag can
maintain up to four simultaneous sessions and a binary Inventoried flag
for each session. Inventory command set includes the following commands:

[0067] Query command can be used to initiate and specify an inventory
round; it contains a slot counter value (Q=0 to 15) determining the
number of slots in the round; the command also includes Sel parameter
specifying which tags should respond to the Query.

[0068] QueryAdjust
command can be used to adjust the value of the tag's slot counter Q
without changing any other parameters;

[0069] QueryRep command can be
used to repeat the last Query command;

[0070] Ack command can be used to
acknowledge a tag's response;

[0071] NAK command can be used to force a
tag to change its state to Arbitrate.

[0072] An RFID tag can implement a state machine. Once energized, a tag
can change its current state to Ready. A selected tag can, responsive to
receiving Query command, select a random integer from the range of [0;
2Q-1]. If the value of zero is selected, the tag can transition to
Reply state, backscattering a 16-bit random number. If a non-zero value
is selected, the tag can load the selected random integer into its slot
counter and change its state to Arbitrate.

[0073] Responsive to receiving the tag transmission, EIR terminal can
acknowledge it with Ack command containing the same random number.
Responsive to receiving Ack command, the tag can change its state to
Acknowledged and backscatter its protocol control (PC) bits, EPC and
cyclic redundancy check (CRC) value. Unacknowledged tag can select a new
random integer from the range of [0; 2Q-1], load the value into its
slot counter, and change its state to Arbitrate. Responsive to receiving
QueryAdjust command, a tag in the Arbitrate state should decrement the
value of its slot counter and backscatter its protocol control (PC) bits,
EPC and CRC value if its slot counter is equal to zero.

[0074] Responsive to receiving the tag's transmission of its PC, EPC and
16-bit CRC value, EIR terminal can send a QueryAdjust command causing the
tag to invert its Inventoried flag and to transition to Ready state.

[0075] Access command set can be used by the EIR terminal 100 for
communicating with (reading from and writing to) a tag. An individual tag
must be uniquely identified prior to access. Access command set includes
the following commands:

[0076] ReqRn command can be used by the EIR terminal 100 to request a
handle from a tag; the handle can be used in the subsequent Access
command set commands. Responsive to receiving Req_RN commands, a tag
returns a 16-bit random integer (handle) and transitions from
Acknowledged to Open or Secured state.

[0077] Read command can be used by the EIR terminal 100 to read tag's
Reserved, EPC, TID and User memory;

[0078] Write command can be used by the EIR terminal 100 to write to tag's
Reserved, EPC, TID and User memory;

[0079] Kill command can be used by the EIR terminal 100 to permanently
disable a tag;

[0081] Access command can be used by the EIR terminal 100 to cause a tag
having a non-zero access password to transition from Open to Secured
state.

[0082] A skilled artisan would appreciate the fact that other methods of
interrogating RFID tags by the EIR terminal 100 are within the scope of
this disclosure.

[0083] One embodiment of the EIR terminal 100 is schematically shown in
FIGS. 7a (front panel view), 7b (side panel view), and 7c (bottom panel
view). The EIR terminal 100 can comprise a housing 52 within which other
components of the EIR terminal 100 can be disposed. An LCD screen display
with a touch screen sensor 554 can be disposed on the front panel 556.
Also disposed on the front panel 556 can be a decode LED 558, a scan LED
559, and a keyboard 64 including a scan key 568 and navigation keys 72.
An imaging window 74 can be disposed on the top panel of housing 52.
Disposed on the side panel (best viewed in FIG. 7b) can be an infra-red
communication port 76, an access door to a secure digital (SD) memory
interface 78, an audio jack 80, and a hand strap 82. Disposed on the
bottom panel (best viewed in FIG. 7c) can be a multi-pin mechanical
connector 84 and a hand strap clip 86. RFID reading device (not shown in
FIGS. 7a-7c) can be disposed within the housing 52.

[0084] While the present invention has been particularly shown and
described with reference to certain exemplary embodiments, it will be
understood by one skilled in the art that various changes in detail may
be affected therein without departing from the spirit and scope of the
invention as defined by claims that can be supported by the written
description and drawings. Further, where exemplary embodiments are
described with reference to a certain number of elements it will be
understood that the exemplary embodiments can be practiced utilizing less
than the certain number of elements.

[0085] A portable radio-frequency identifier (RFID) reading terminal can
comprise a microprocessor, a memory, an RFID reading device, and a
display. The portable EIR terminal can be configured, responsive to
successfully reading a plurality of RFID tags attached to a plurality of
items sustained by a physical structure, to group the plurality of read
RFID tags into zero or more clusters, by correlating quantities of RFID
tags read within several time periods to spatial positions of the
coverage shapes of the RF signals transmitted by the RFID reading device
during the several time periods. The EIR terminal can be further
configured to determine the spatial positions of the RFID signal coverage
shapes based on the spatial positions and orientations of the portable
EIR terminal during the several time periods. The EIR terminal can be
further configured to display a quantity of RFID tags within each cluster
overlaid over an image of the physical structure, with a visual reference
to a fragment of the physical structure corresponding to the spatial
positions of the RFID tags comprised by each cluster.

[0086] A small sample of systems, methods, and apparata that are described
herein is as follows:

[0092] wherein said portable EIR terminal is configured, responsive to
successfully reading a plurality of RFID tags attached to a plurality of
items sustained by a physical structure, to group said plurality of read
RFID tags into zero or more clusters, by correlating quantities of RFID
tags read within several time periods to spatial positions of coverage
shapes of RF signals transmitted by said RFID reading device during said
several time periods, said spatial positions of said coverage shapes of
said RFID signals determined based on spatial positions and orientations
of said portable EIR terminal during said several time periods;

[0093] wherein said portable EIR terminal is further configured to display
a quantity of RFID tags within each cluster overlaid over an image of
said physical structure, with a visual reference to a fragment of said
physical structure corresponding to spatial positions of one or more RFID
tags comprised by each cluster.

[0094] A2. The portable EIR terminal of (A1), further configured to
display a scan trace overlaid over said image of said physical structure;

[0095] wherein said scan trace is provided by a line comprising a
plurality of time varying points, each point being defined by a
projection onto a chosen plane at a given moment in time of said coverage
shape of said RF signal transmitted by said RFID reading device.

[0096] A3. The portable EIR terminal of (A1), further comprising a
two-dimensional imager;

[0097] wherein said portable EIR terminal is further configured to
determine a spatial position of said RF signal coverage shape based on a
position and orientation of said RF antenna relatively to a position of a
field of view of said two-dimensional imager.

[0099] wherein said portable EIR terminal is further configured to
determine a change of a spatial position and orientation of said RF
signal coverage shape based on motion sensing data received from said
motion sensing device.

[0101] wherein said motion sensing device comprises three or more
accelerometers configured to measure proper acceleration values of said
EIR terminal along three mutually perpendicular axes.

[0102] A6. The portable EIR terminal of (A1), further configured to
receive an image of said physical structure from an external computer.

[0103] A7. The portable EIR terminal of (A1), further configured to
receive a description of a physical structure;

[0104] wherein said portable EIR terminal is further configured to create
an image of said physical structure based on said description.

[0105] A8. The portable EIR terminal of (A1), further comprising a
two-dimensional imager;

[0106] wherein said portable EIR terminal is further configured to acquire
an image of said physical structure using said two-dimensional imager.

[0107] A9. The portable EIR terminal of (A1), further configured to
transmit to an external computer at least one of: a list of read RFID
tags, a count of read RFID tags, a count of clusters of RFID tag bearing
items, a list of items in each cluster, and/or a list of locations of
clusters to an external computer.

Patent applications by Philip Zumsteg, Shorewood, MN US

Patent applications by Honeywell International Inc. doing business as (d.b.a) Honeywell Scanning and Mobility